FIGS. 1 and 2 illustrate a prior art continuous process steam cooker and blancher, generally designated by the reference numeral 10. Cooker/blancher 10 is capable of cooking or blanching a continuous flow of bulk food particles such as diced potatoes or other vegetables. Cooker/blancher 10 includes a frame 12, an outer cover 14, and a lower drip pan 16. Outer cover 14 seals over lower drip pan 16 to form a steam housing 18. Steam housing 18 rests atop frame 12. Outer cover 14 and lower drip pan 16 are insulated to conserve heat within steam housing 18. Drains 19 are provided in lower drip pan 16 to allow condensed water to escape steam housing 18.
An endless belt conveyor 22 is mounted in housing 18 and extends from an infeed end to an outfeed end. A conveyor drive motor 32 is connected to a set of drive rollers 30 by a conveyor drive belt (not shown) to drive belt conveyor 22. A conveyor support rail 36 runs longitudinally beneath the upper run of belt conveyor 22 at its lateral edges to provide vertical support to belt conveyor 22 along its length.
Outer cover 14 includes opposed inner sidewalls 38 which extend longitudinally above the lateral edges of belt conveyor 22. Sidewalls 38 extend within steam housing 18 along the entire length of belt conveyor 22 and outer cover 14 to contain a depth of bulk food particles 41 on belt conveyor 22 between sidewalls 38 and to seal between the inner sidewall and the belt conveyor.
Infeed and outfeed rotary airlock valves 42 and 44 are attached to the extreme longitudinal ends of steam housing 18 to allow food particles 41 to enter and exit steam housing 18 while maintaining a sealed atmosphere within steam housing 18. Each of rotary valves 42 and 44 contains a lateral shaft to which a plurality of radially extending blades are attached. The shaft and attached blades rotate to transfer food particles through the rotary valve without allowing steam to escape from steam housing 18.
Infeed rotary valve 42 has an upper hopper 48 which funnels food particles into rotary valve 42. A lower chute (not shown) directs food particles from rotary valve 42 onto belt conveyor 22 at its infeed end. Outfeed rotary valve 44 at the outfeed end has an upper mouth 52 which receives food particles as they fall from the end of belt conveyor 22 and which funnels the food particles into outfeed rotary valve 44 for transfer from steam housing 18.
Rotary valve 42 feeds a continuous flow of bulk food particles 41 onto belt conveyor 22. The particles accumulate to a desired depth and travel through steam housing 18 between sidewalls 38 on belt conveyor 22, eventually falling off belt conveyor 22 and into upper mouth 52 of outfeed rotary valve 44 for transfer from steam housing 18.
Steam manifold elements 80 within steam housing 18 above belt conveyor 22 spray steam onto food particles 41 as they pass through steam housing 18. The steam maintains a constant temperature within steam housing 18 of about 212 degrees Fahrenheit. This temperature is sufficient to cook or blanch the bulk food particles within steam housing 18. Cooking duration can be varied by controlling the speed of conveyor 22 and the corresponding time required for the food particles to travel the entire length of steam housing 18.
A problem with the continuous process steam cooker and blancher described above is that the depth of product on belt conveyor 22 must be limited to insure even heat distribution from top to bottom of the product depth. If the food particles on the belt conveyor have too great a depth, the uppermost particles will achieve much greater heating and cooking than the lower particles.
The invention described below overcomes this problem, providing even heating and cooking throughout a much greater depth of food particles without increasing retention time within the cooker/blancher. In fact, retention time can often be decreased, even with a greater product depth. In either case, the invention result in greater product capacity in comparison to the prior art apparatus described above.